In the field of solid state light sources such as LEDs, it is commonly known to directly connect the light sources to mains voltage supply. In order to provide a stable drive current to the solid state lighting devices from the mains voltage driver units are necessary. Usually a rectified pulsating mains voltage is provided as drive voltage to the LEDs in order to power the LEDs, however, the driver devices have to ensure that the LEDs are not switched off during the zero crossing of the mains voltage to avoid that flickering light is emitted by the light unit.
In order to avoid a flicker of the emitted light, a charge capacitor is usually connected in parallel to the LEDs to provide electrical power during the zero crossing to the LEDs. Alternatively a tapped linear driver can be used, wherein also a corresponding charge capacitor is necessary in parallel to the LED units in order to provide electrical power to the LEDs during the zero crossing of the mains voltage.
The charge capacitors which provide the electrical power during the zero crossing have a large size since these charge capacitors have to be designed for high voltages around 400 V for 230 V mains voltage, so that the size of the LED unit is increased in general.
US20130313984A1 discloses a circuit for actuating a plurality of light-emitting means, wherein least one energy store is connected in parallel with a first group of light-emitting means during a charge phase, and is connected in parallel with a second group of light-emitting means during a discharges phase.